In one form of releasable push-to-connect tube fitting, a collet is received within an end portion of the fitting body. The tube end is coaxially inserted through the collet for effecting a sealed connection of the tube end to the fitting body.
A number of different fittings have been developed for effecting such a tube connection. Illustratively, in U.S. Pat. No. 3,909,046 of Andre Legris, a tube fitting is shown wherein a tubular collet is firstly installed in a tubular member having at its axially inner end a tapered camming surface. The collet is installed from the inner end of the tubular member and, thus, the outer end of the collet must be no bigger than the minimum diameter of the bore of the tubular member. Resultingly, as shown in the Legris patent, it is difficult to release the tube from the fitting as such release requires the forceful urging of the collet axially inwardly as by a screwdriver acting on the relatively small distal end of the collet projecting from the fitting. In addition, the tubular member must be fixedly secured in the fitting body, thereby increasing the cost of the fitting and further providing a potential area of failure of the fitting should the tubular member not remain fixedly secured in the body.
Another collet-type tube coupling is illustrated in U.S. Pat. No. 4,178,023 of John D. Guest. As shown therein, the collet is provided with slots, permitting the inner end of the collet to be sufficiently compressed so as to permit it to pass axially inwardly through the small end of a tapered bore of the fitting body. This permits the collet to be assembled from outside the fitting body and permits the outer end of the collet to have a relatively large turned flange so as to permit facilitated axially inward movement of the collet in releasing the tube end from the fitting when desired. This design, however, has the serious disadvantage of potentially permitting the outward movement of the collet when the fitting is subjected to substantial fluid pressures as it is the resiliency of the slotted end of the collet which is retaining the collet in the fitting. The change of such failure is further increased where the tubing is of relatively soft material, such as synthetic resins, which offer relatively small resistance to radial inward constriction of the slotted collet end.